Table of Contents

Blob detection

One approach for blob detection is the detection of local maxima of the Laplacian filter response in the scale space of the input image.

This means that you:

you first construct a scale-space = image pyramid with N levels (= 'octaves') and on each level of the image pyramid you generate blurred version of the image with different blurring levels

you filter each such blurred image with the Laplacian filter

you detect local maxima (minima) of these filter responses, where a blob has to be a local maximum not only in the same image (8 neighbours), but also compared to neighboured scales (2×9 neighbours), i.e. in total 8+18=26 neighbours are considered